Segmented flexible gel composites and rigid panels manufactured therefrom

ABSTRACT

The present invention describes various methods for manufacturing gel composite sheets using segmented fiber or foam reinforcements and gel precursors. Additionally, rigid panels manufactured from the resulting gel composites are also described. The gel composites are relatively flexible enough to be wound and when unwound, can be stretched flat and made into rigid panels using adhesives.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application from U.S. patentapplication Ser. No. 13/800,551, filed on Mar. 13, 2013; which claimsthe benefit from U.S. Provisional Patent Application 61/682,198 filed onAug. 10, 2012, which are all hereby incorporated by reference in theirentirety as if fully set forth.

SUMMARY OF THE INVENTION

The present invention describes a process of manufacturing a fiberreinforced gel composite comprising the steps of, providing a segmentedfiber batting sheet, combining the batting with a gel precursor, gellingthe combination to make a composite, rolling the composite; and dryingthe composite to make a fiber reinforced gel composite. Additionally,further steps of unrolling the dried composite, applying an adhesive toat least one side of the composite and attaching it to another planarmaterial may be carried out.

Additionally, a process of manufacturing a gel composite panel isdescribed which comprises the steps of, providing a dried, segmentedfiber-reinforced gel composite sheet with at least two major surfacesand multiple segmented cross-sectional surfaces, applying an adhesive toat least one surface of said composite; and attaching said composite toanother dried, segmented gel composite.

Additionally, a process of manufacturing a reinforced gel composite isdescribed which comprises the steps of, providing a segmented open cellfoam sheet, combining the batting with a gel precursor, gelling thecombination to make a composite, rolling the composite; and drying thecomposite to make a reinforced gel composite. The segmented fiberbatting or the segmented open cell foam sheet of any of the precedingprocesses may have a facing layer or facing sheet attached to them. Suchfacing layers may comprise fibers. The fiber battings or non-wovens ofthe processes of the present invention may comprise non-continuousfibers or continuous filaments.

Additionally, the above described processes involve the step ofincorporating additives into the composite selected from the groupconsisting of titanium dioxide, iron oxides, carbon black, graphite,aluminum hydroxide, phosphates, borates, metal silicates, metallocenes,molybdates, stannates, hydroxides, carbonates, zinc oxides, aluminumoxides, antimony oxides, magnesium-zinc blends, magnesium-zinc-antimonyblends, silicon carbide, molybdenum silicide, manganese oxides, irontitanium oxide, zirconium silicate, zirconium oxide, iron (I) oxide,iron (III) oxide, manganese dioxide, iron titanium oxide (ilmenite),chromium oxide and a combination thereof.

Additionally, the above processes involve the step of adding at least abinder to the fibers or using a fibers or fiber systems comprising atleast one binder. The processes of the present invention involve the useof segmented fiber battings with at least one segment being rigid.

Additionally, the processes of the present invention use as gel in thefiber reinforced gel composite, one or more material or derivativesthereof selected from the group consisting of zirconia, yttria, hafnia,alumina, titania, ceria, silica, polyacrylates, polystyrenes,polyacrylonitriles, polyurethanes, polyimides, polyfurfural alcohol,phenol furfuryl alcohol, melamine formaldehydes, resorcinolformaldehydes, cresol formaldehyde, phenol formaldehyde, polyvinylalcohol dialdehyde, polycyanurates, polyacrylamides, various epoxies,agar, and agarose and combinations thereof.

The fibers in the fiber batting sheet, facing layer or the segmentedfiber reinforced gel composites of the present invention comprise one ormore materials selected from the group consisting of mineral wool, glasswool, rock wool, fiber glass, polyester, polyolefin terephthalates,poly(ethylene) naphthalate, polycarbonates and Rayon, Nylon, cottonbased lycra (manufactured by DuPont), Carbon based fibers like graphite,precursors for carbon fibers like polyacrylonitrile (PAN), oxidized PAN,uncarbonized heat treated PAN such as the one manufactured by SGLcarbon, fiberglass based material like S-glass, 901 glass, 902 glass,475 glass, E-glass, silica based fibers like quartz, quartzel(manufactured by Saint-Gobain), Q-felt (manufactured by Johns Manville),Saffil (manufactured by Saffil), Durablanket (manufactured by Unifrax)and other silica fibers, Polyaramid fibers like Kevalr, Nomex, Sontera(all manufactured by DuPont) Conex (manufactured by Taijin), polyolefinslike Tyvek (manufactured by DuPont), Dyneema (manufactured by DSM),Spectra (manufactured by Honeywell), other polypropylene fibers likeTypar, Xavan (both manufactured by DuPont), fluoropolymers like PTFEwith trade names as Teflon (manufactured by DuPont), Goretex(manufactured by GORE), Silicon carbide fibers like Nicalon(manufactured by COI Ceramics), ceramic fibers like Nextel (manufacturedby 3M), Acrylic polymers, fibers of wool, silk, hemp, leather, suede,PBO—Zylon fibers (manufactured by Tyobo), Liquid crystal material likeVectan (manufactured by Hoechst), Cambrelle fiber (manufactured byDuPont), Polyurethanes, polyamaides, Wood fibers, Boron, Aluminum, Iron,Stainless Steel fibers and other thermoplastics like PEEK, PES, PEI,PEK, PPS and combinations thereof.

Additionally, the processes for making panels described in the presentinvention make use of one or more of the adhesives selected from thegroup consisting of potassium water glass, sodium water glass, cementand alkali-activated aluminosilicates, polyethylene, kapton,polyurethane, polyester, natural rubber, synthetic rubber, hypalon,plastic alloys, PTFE, polyvinyl halides, polyester, neoprene, acrylics,nitriles, EPDM, EP, viton, vinyls, vinyl-acetate, ethylene-vinylacetate, styrene, styrene-acrylates styrene-butadienes, polyvinylalcohol, polyvinylchloride, acrylamids, phenolics and combinationsthereof. The thermal conductivity of the reinforced gel composites madefrom the above processes is less than 25 mW/mK at ambient conditions.

A segmented fiber reinforced gel composite is described wherein the gelis continuous through the fiber in at least one segment and at least onegap exists between at least two adjoining segments. A gap as describedhere means there is a discontinuity in both the fiber and the gel ofthese adjoining segments.

Additionally, a rigid panel is described comprising at least two layersof fiber reinforced gel composites wherein at least one layer comprisessegmented fiber reinforced gel composite with at least a gap in bothfiber and gel between at least two adjoining segments.

In an embodiment, the gel composites or the panels of the presentinvention further comprising fillers selected from the group consistingof titanium dioxide, iron oxides, carbon black, graphite, aluminumhydroxide, phosphates, borates, metal silicates, metallocenes,molybdates, stannates, hydroxides, carbonates, zinc oxides, aluminumoxides, antimony oxides, magnesium-zinc blends, magnesium-zinc-antimonyblends, silicon carbide, molybdenum silicide, manganese oxides, irontitanium oxide, zirconium silicate, zirconium oxide, iron (I) oxide,iron (III) oxide, manganese dioxide, iron titanium oxide (ilmenite),chromium oxide and a combination thereof. In another embodiment, thepanels or composites of the present invention further comprise at leasta binder in the fiber structure.In another embodiment, the segmented fiber batting or segmented opencell foam sheets of the panels or composites of the present inventionhave a facing layer or sheet attached. The face sheet layer may comprisefibers. The fiber battings of the present invention may comprisenon-continuous fibers or continuous filaments or a combination thereof.

Additionally, the panels or composites of the present invention mayfurther comprise additives selected from the group consisting oftitanium dioxide, iron oxides, carbon black, graphite, aluminumhydroxide, phosphates, borates, metal silicates, metallocenes,molybdates, stannates, hydroxides, carbonates, zinc oxides, aluminumoxides, antimony oxides, magnesium-zinc blends, magnesium-zinc-antimonyblends, silicon carbide, molybdenum silicide, manganese oxides, irontitanium oxide, zirconium silicate, zirconium oxide, iron (I) oxide,iron (III) oxide, manganese dioxide, iron titanium oxide (ilmenite),chromium oxide or a combination thereof.

Additionally, the panels or composites of the present invention mayfurther comprise at least a binder in the fibers or use a fibercomprising at least one binder. At least a segment of the segmentedfiber batting may be rigid in the preceding panel or composites.

Additionally, the panels or composites of the present invention havecomponents that are made from the gel precursors of zirconia, yttria,hafnia, alumina, titania, ceria, silica, polyacrylates, polystyrenes,polyacrylonitriles, polyurethanes, polyimides, polyfurfural alcohol,phenol furfuryl alcohol, melamine formaldehydes, resorcinolformaldehydes, cresol formaldehyde, phenol formaldehyde, polyvinylalcohol dialdehyde, polycyanurates, polyacrylamides, various epoxies,agar, and agarose and combinations thereof.

Additionally, the fibers in the panels or composites of the presentinvention are selected from the group consisting of mineral wool, glasswool, fiber glass, polyester, polyolefin terephthalates, poly(ethylene)naphthalate, polycarbonates and Rayon, Nylon, cotton based lycra(manufactured by DuPont), Carbon based fibers like graphite, precursorsfor carbon fibers like polyacrylonitrile (PAN), oxidized PAN,uncarbonized heat treated PAN such as the one manufactured by SGLcarbon, fiberglass based material like S-glass, 901 glass, 902 glass,475 glass, E-glass, silica based fibers like quartz, quartzel(manufactured by Saint-Gobain), Q-felt (manufactured by Johns Manville),Saffil (manufactured by Saffil), Durablanket (manufactured by Unifrax)and other silica fibers, Polyaramid fibers like Kevalr, Nomex, Sontera(all manufactured by DuPont) Conex (manufactured by Taijin), polyolefinslike Tyvek (manufactured by DuPont), Dyneema (manufactured by DSM),Spectra (manufactured by Honeywell), other polypropylene fibers likeTypar, Xavan (both manufactured by DuPont), fluoropolymers like PTFEwith trade names as Teflon (manufactured by DuPont), Goretex(manufactured by GORE), Silicon carbide fibers like Nicalon(manufactured by COI Ceramics), ceramic fibers like Nextel (manufacturedby 3M), Acrylic polymers, fibers of wool, silk, hemp, leather, suede,PBO—Zylon fibers (manufactured by Tyobo), Liquid crystal material likeVectan (manufactured by Hoechst), Cambrelle fiber (manufactured byDuPont), Polyurethanes, polyamaides, Wood fibers, Boron, Aluminum, Iron,Stainless Steel fibers and other thermoplastics like PEEK, PES, PEI,PEK, PPS and combinations thereof.

Additionally, the panels of the present invention include adhesivesselected from the group consisting of potassium water glass, sodiumwater glass, cement and alkali-activated aluminosilicates, polyethylene,kapton, polyurethane, polyester, natural rubber, synthetic rubber,hypalon, plastic alloys, PTFE, polyvinyl halides, polyester, neoprene,acrylics, nitriles, EPDM, EP, viton, vinyls, vinyl-acetate,ethylene-vinyl acetate, styrene, styrene-acrylates styrene-butadienes,polyvinyl alcohol, polyvinylchloride, acrylamids, phenolics andcombinations thereof. In an embodiment, the panels or composites of thepresent invention have an apparent thermal conductivity of less than 25mW/mK at ambient conditions.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1. illustrates aerogel composite produced using a rotary-glassnon-woven as-is (without segmentation).

FIG. 2. illustrates schematic depicting the manufacture of aerogelcomposites using scored non-woven products with increased rigidity.

FIG. 3. illustrates a comparison of the dried gel composites producedwith non-segmented glass wool sheet (above) and with segmented glasswool sheet (below).

FIG. 4. illustrates segmented wet gel composite and the segmented drygel composite.

FIG. 5. illustrates panelization of segmented aerogel/fiber compositeinto Board stock.

FIG. 6. illustrates-manufacturing of rigid panels starting fromsegmented fiber-reinforcement sheets and gel precursors.

FIG. 7. illustrates an alternative embodiment of the fiber reinforcementwhere there is a gradual change in segment sizes along the length of thefiber reinforcement

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves manufacturing of rolled insulationproducts based on aerogels and aerogel-like materials. Aerogels, whichexhibit extremely low density, high surface area, good optical, thermal,and acoustic properties, have been explored for various applications.However, aerogels have inherent drawbacks such as weakness andbrittleness. Various types of reinforcements may be used to addstrength, flexibility and other important properties to aerogels. Fiberreinforced aerogel composites may be made from adding loose fibers ornon-woven fiber sheets to the gel precursors, gelling the combination tomake a gel sheet, aging the gel sheet and drying the formed gel sheet.

Aerogels, which exhibit extremely low density, high surface area, goodoptical, thermal, and acoustic properties, have been used previously totry to address this need and other needs for which their propertiescould be advantageous. However, aerogels have inherent drawbacks such asweakness and brittleness. Notably, when making highly transparent andhydrophobic aerogels, brittleness becomes much more acute, and thus theyare more difficult to handle, and require long cycle times for fluiddrying in order to avoid cracking.

The weakness and brittleness of low density aerogels can particularlyhave a negative impact on production scale-up and limit large scalemanufacturing. Additionally, aerogels with lower densities may have thebest transparency, but also exhibit higher thermal conductivity andthus, exhibit worse insulation performance.

The fragile structure of an aerogel (low density and high porosity) alsoposes several difficulties in conforming to irregular surfaces, ormaintaining integrity in dynamic conditions such as when sandwichedbetween glass and different thermal expansion coefficients between glassand aerogel results in compressive forces. So, flexibility,compressibility, integrity, durability, strength, and resistance tosintering, dusting and cracking are all areas for potential improvementin aerogels and aerogel composites.

A number of attempts have been made to improve aerogels and aerogelcomposites to address these problems and take fuller advantage of theirremarkable properties as materials. Some patents describe attempts tomake composites with foams and particulate aerogels, for example,EPO489319, and U.S. Pat. Nos. 6,136,216; 5,691,392; 6,040,375; and6,068,882. Others, for example, U.S. Pat. Nos. 4,966,919; 5,037,859;5,972,254; 5,973,015; and 6,087,407; and US Patent ApplicationPublication No. 2002/0094426 describe other aerogel or aerogelcomposites with or without foams. Some, such as US Patent ApplicationPublication No. 2005/0192367 and U.S. patent application Ser. No.11/392,925 describe transparent aerogels or aerogel composites.

Within the context of embodiments of the present invention “aerogels” or“aerogel materials” along with their respective singular forms, refer togels containing air as a dispersion medium in a broad sense, and gelsdried with supercritical fluids in a narrow sense. The chemicalcomposition of aerogels can be inorganic, organic (including polymers)or hybrid organic-inorganic. Inorganic aerogels may be based on Silica,Titania, Zirconia, Alumina, Hafnia, Yttria, Ceria, Carbides andNitrides. Organic aerogels can be based on compounds including but arenot limited to: urethanes, resorcinol formaldehydes, polyimide,polyacrylates, chitosan, polymethylmethacrylate, members of the acrylatefamily of oligomers, trialkoxysilyl terminated polydimethylsiloxane,polyoxyalkylene, polyurethane, polybutadiane, melamine-formaldehyde,phenol-furfural, a member of the polyether family of materials orcombinations thereof. Examples of organic-inorganic hybrid aerogelsinclude, but are not limited to: silica-PMMA, silica-chitosan,silica-polyether or possibly a combination of the aforementioned organicand inorganic compounds. Published US patent applications 2005/0192367and 2005/0192366 teach extensively of such hybrid organic-inorganicmaterials and are hereby incorporated by reference in their entirety.

Aerogels applicable to the present invention include such aerogels whichare reinforced by a fibrous structure. Such reinforcements providestrength and flexibility to the aerogel structure. U.S. Pat. Nos.6,068,882, 6,087,407, 6,770,584, 5,124,101,5973015, 6479416, 5789075,5866027, 5786059, 5972254, 4363738, 4447345, PCT application WO9627726,U.S. patent applications 20020094426, 2003077438, Japanese patentJP8034678, U.K. Patent GB1205572 teach some of the aerogel materialsthat may be practiced with the embodiments of the present invention.These documents are incorporated herein by reference to teach themethods of manufacturing such flexible aerogel materials, at least inpart. Flexible aerogel materials can also have form factors that areblankets or thin strips. Although many of the embodiments of the presentinvention are focused towards coating aerogel composites, they can alsobe used to coat other forms of aerogels.

Fiber reinforcement when applied appropriately results in flexibleaerogel materials. Such flexibility in aerogel materials is desirable ina variety of applications where said aerogel materials can bedrop-in-replacements for the existing materials. However, flexibilitysometimes may also result in certain damage to the aerogel structure.Though it may not affect other critical properties of aerogel materials,it can present a nuisance to physical handling. The present invention,in many of its embodiments provides methods to minimize the effects ofsuch damage and further prevent any such damaged material fromdislodging from the material matrix. Hence, any consequential mechanicalhandling issues related to aerogel particulate materials on the surfaceof such aerogel material are avoided and substantially reduced by themethods of the present invention.

It has been shown that the retrofit of existing homes, buildings andstructures with insulation possessing high thermal resistance cansignificantly reduce energy consumption and corresponding CO₂ emissions.There has thus been a strong desire to develop aerogel-based insulationmaterials for the building and construction market. For applications notinvolving cavity wall and/or lofted attic insulation, a preferredproduct for this market is rigid panels. For instance, many interior orexterior retrofits of buildings involve the installation of non-flexibleboard stock such as mineral wool or EPS foam. Over the past decade,there has been a renewed interest in producing rigid panels with thermalinsulation materials with greater R-values than that currently on themarket. High performance aerogel-based insulation has been of particularinterest. Fiber reinforced aerogel insulation is currently commerciallyavailable in high volume as a flexible durable composite blanket atthicknesses not exceeding 10 mm. Multiple plies of these materials aretypically laminated with adhesives to produce a rigid board of greaterthickness. Because flexible aerogel based insulation is necessarilyproduced as a rolled-good, it may possess a certain degree of windingdefects in the form of buckles, undulations and/or thickness variationsand as such extensive process and quality control needs to be employedto manage these issues. The presence of these defects makes thelamination of flexible aerogel materials into rigid board stock achallenge. Individual layers of aerogel insulation with surface defectsresult in an incomplete surface bond due to the inability to attain fullsurface mating of each individual ply during the lamination process.Panels produced in such a fashion may contain a large number of voidsand defects that not only affect mechanical strength but also overallthermal performance. There thus exists a strong need to eliminate thesurface defects of these materials that are due mainly to the stressesimposed by winding and unwinding, stresses typically associated with themanufacture of rolled goods. The winding and unwinding processassociated with the production of flexible composite aerogel insulationalso presents challenges for the use of rigid fibrous based materials asreinforcement for these composites. Fibrous materials with high bindercontent and/or materials that are rigid cannot sustain thewinding/unwinding process of rolled-good manufacture without sustainingcopious amounts of defects in the form of delaminations, buckles and/ortears. Due to substantially improved economics, there is a strong desireto enable the use of lower cost fibrous reinforcements with high bindercontent for the production of flexible aerogel insulation. To date,these types of reinforcement materials are too rigid to be wound arounda mandrel with a small radius without imparting non-conformities in thepresence of folds, tears and delaminations. As such, there is a need todevelop a process that could enable the winding and subsequent aerogelprocessing of such material without imparting the damage associated withwinding. For the purposes of this patent application, a rigid panelmeans a panel of practical installable surface area (from 0.1 to 10 m²)with the ability to hold its own weight without bending to the extentthat it interferes in the practical handling and installation of thepanel. While one can make rigid panels by attaching non-rigid planarmaterial to another rigid material, the rigid panel as defined aboveexcludes such attached combinations and the rigid panels of the presentinvention focuses on one or more gel-composite layers attached throughadhesives or otherwise being rigid as described above.

The present invention also describes an efficient method to manufactureflat-panel aerogel-based boards using low-cost fibrous substrates withincreased rigidity. Such substrates are not normally amenable tostandard processing in a cylindrical vessel for the various processesinvolved in manufacturing gel composites in rolled good form. Efficientutilization of vessels necessitates the manufacture of fiber reinforcedaerogel materials in rolled good form in order to maximize the volume ofa cylindrical vessel and reduce the fixed costs associated withproduction. As such, the fiber reinforcements used to reinforce aerogelsneed to have sufficient flexibility to sustain winding and unwinding.Materials with excess rigidity and/or materials with high binder contentdo not normally process well and typically result in the manufacture ofaerogel composites with excessive defects in the form of folds, buckles,delaminations and tears (FIG. 1). The final product formed using suchrigid reinforcements is thus not amenable to the production offlat-panel board stock, a preferred product form for building andconstruction applications. The excessive amount of defects in suchproducts diminishes thermal performance, material integrity and severelycomplicates any fabrication process.

We have discovered that the longitudinal segmentation (across the widthof the blanket) of rigid non-woven fiber reinforcement enablessufficient flexibility so that the product can be wound/unwound withminimal delamination or buckling. In another embodiment, a facing sheetis integrated on one side of the blanket to provide additional tensilestrength. Segmented non-woven blankets may be prepared by variousmethods including scoring the non-woven partially across its thickness,attaching separate segments to a face sheet, thus creating a segmentedsheet connected together by the face sheet, scoring the non-woven sheetall the way and attaching a face sheet or any other practical ways knownin the art. The terms segmentation and scoring are used interchangeablyin this document to refer to the process of making segmented sheets inwhich segments are held together by a face sheet. Alternatively, thescoring (cutting) is performed for less than the thickness of the sheetssuch that the segmented sheet is still in one piece and held together bythe portions through the thickness not cut by the scoring process.Certain scored non-woven sheets are available in the market. An exampleis a mineral wool non-woven, Isoroll MW from Isolparma S.r.l. Thesegmented non-woven sheet is carried by a face sheet/veil through thefiber-reinforced aerogel composite production process and the subsequentfabrication of rigid panel—see schematic in FIGS. 2 and 6. The non-wovenfiber reinforcement can be efficiently wound in a cylindrical form andany gel-infused sheets manufactured therefrom may be unwound into a flatboard-like shape with little to no damage. This allows for the efficientcasting of a wet gel/fiber composite using a flat conveyor belt and thewinding of the final wet-gel composite to enable efficient utilizationin processes involving the use of cylindrical vessels. Alternatively,segmented non-woven sheet may be pre-wound with another non-permeablelayer adjoining its major surface and a gel precursor may be infusedinto the fiber matrix along the axis of the winding, subsequentlyunwound after gel formation and further processed to produce a drysegmented gel composites. More importantly, most of the visible air gapsin the gel composite as produced in the cylinderical form, betweenadjoining segments, effectively disappear upon unwinding into flatstock, ensuring that thermal performance of a typical aerogel-fibercomposite is maintained. The final material can be unwound into a nearperfect flat panel, enabling the efficient production of rigid panels oraerogel-based boards suitable for building and constructionapplications. What was surprising and unexpected was that when wound(either as wet or dry gel), the gaps, i.e. gaps between two adjoiningsegments separated in a clean line without shattering the wet or driedgel. Aerogels and other dried gels made from the gel precursorsdescribed in the present invention are fragile material that whensubjected to any stress are prone to crack and shatter. However, what wehave found here is a process where the dried gels can be broken in cleanlines at the gaps such that when subsequently unwound, they produce asubstantially planar surface. This allows for efficient manufacturing offlat panels. Furthermore, individual segments are still rigid, even ifthey are amenable to be wound and unwound. This segment rigidity allowsfor the manufacturing of rigid panels with two or more of suchmanufactured fiber reinforced gel composite sheets using adhesives ofvarious kind, using a non-adhesive mechanical fasteners, needling of theproduced composites or sewing them using extraneous fibers.

We have reduced this invention to practice by producing small scalerolls of aerogel composites measuring 36″ length and 8″ width.Specifically, we have used segmented rotary-glass based glass woolsheet, to produce gel composite materials in a rolled good process. Thenon-woven and the gel composites were wound around a mandrel of 6″diameter. Using standard silica aerogel precursors (Tetraethoxysilaneand its derivatives), wet gel composites were produced using this glasswool sheet (scored or segmented at 1 or 2″ intervals along its length)and were subsequently rolled around a 6″ diameter after a 12 minuteperiod of syneresis. Upon winding, the wet gel cleanly fractures at thescores (or segmentations) to enable flexibility and maintain theintegrity of the fiber/aerogel segments (FIG. 4).

The wound wet gel/fiber composite is now amenable to processing in acylindrical vessel for aging, rinsing and supercritical CO2 extractionand is in an ideal shape to maximize the volume of a cylindrical vessel.After removal of solvent via supercritical CO2 extraction, the materialmaintains sufficient flexibility such that it can be unwound into flatstock (Figure ?). In contrast to aerogel composites produced withnon-segmented glass wool sheet of the same type, the use of a segmentedglass wool sheet has significantly reduced/eliminated any materialdefects associated with winding and unwinding steps. The segmented gelcomposite maintains flexibility such that it can be unwound andpanelized to produce a board stock (FIGS. 4, 5 and 6).

We have also successfully demonstrated that the use of the segmentedaerogel/fiber composite can be used to produce flat board stock usinginorganic or organic adhesives. Specifically, we have producedprototypes using potassium silicate adhesives and two plies of segmentedaerogel/fiber composites. The original purpose of the face sheet in theraw fiber reinforcement was to provide improved tensile strength and acarrier for the segments of fiber, but we have also discovered that suchface sheet can now be oriented outwards to provide some level of dustcontainment for the final aerogel board stock.

Aerogel production processes involving the use of high pressuresnecessarily involve cylindrical pressure vessels. Even low pressuresteps such as aging or rinsing are efficiently carried out usingcylindrical vessels. Fluid handling is easier in cylindrical vesselsthan vessels of any other shape. In order to fully maximize the use acylindrical vessel, one must process a flexible gel composite such thatit adopts a cylindrical-like shape and thus fills any vessel to nearly100% of the available volume. In order to accomplish this, the fiberreinforcement of the aerogel composite must be able to sustain windingand unwinding and must conform without failure to small radius on theorder of 3-18 inches. The present invention enables non-woven fiberreinforcements that are sufficiently rigid, or non-woven fiberreinforcements typically containing appreciable amounts of binder to beused as reinforcements for manufacturing aerogel/fiber composites.Because these non-woven materials are typically lower in cost than theother types of non-wovens (i.e. needlepunched), the present inventionhas the capability of substantially lowering the cost offiber-reinforced gel composite insulation.

In another embodiment, an integrated process is provided for making arigid panel from segmented non-woven reinforcement materials (FIG. 6). Asegmented non-woven sheet (1) is unrolled onto a moving conveyer beltand gel precursor in a liquid form is applied on top of the unrollednon-woven and allowed to infuse into the non-woven to become a gel sheetduring its travel through the conveyor belt. At the end of the conveyorbelt, the gel-infused non-woven (a wet gel composite sheet) is rolledonto a mandrel (2). This rolling may visibly show the gaps between thesegments. Thus rolled wet gel composite is transferred to a vessel toallow the aging to take place resulting in a gel composite with variousdesired strength and other properties. Optionally, the rolls may berinsed with a solvent and in yet another embodiment treated withhydrophobic agents to impart surface hydrophobicity. The roll issubsequently dried using various methods including ambient pressure,subcritical, supercritial carbon dioxide drying. The dried gel may beoptionally carried through an oven to further remove any residualsolvent or water. Thus dried two gel composite rolls are unrolled asillustrated in the FIG. 5 (bottom) with segmented side of the sheetssimultaneously applied with an adhesive (5). The adhesive may be anorganic or an inorganic adhesive. After the application of the adhesive,the rolls are joined together and passed between a pair of rotating niprollers where the two gel-composite layers are compressed together.Additional nip rollers (4) may be added to this set up depending on theadhesive used and the compression needed to make the sheets into rigidpanels (6). Thus formed rigid panels may be cut into desired sizes andpackaged for shipment or for additional inspection and furtherprocessing or drying as appropriate.

In another embodiment, the segmented fiber reinforcement sheet may beprepared such that the size of the segments along the length are notuniform. Specifically, the segment sizes may be gradually increased.This helps in winding the gel-sheets prepared from such reinforcementsheets where winding creates a gradually increasing radius of curvature.A segmented fiber reinforcement sheet illustrating this embodiment isshown in FIG. 7.

In another embodiment, instead of using a segmented fiber reinforcementsheet, a non-segmented or partially segmented reinforcement sheet may beused to make a gel sheet which may be segmented after the gel sheet ismade. In this case, a rigid or moderately rigid fiber reinforcementsheet may be combined with gel precursors and allowed to gel as a gelsheet. Such gel sheet may be scored (or cut) such that segmentationsarea created in the gel sheet. On winding, this segmented gel sheetbehaves similar to the segmented gel sheets made from segmented fiberreinforcement. Alternatively, even when a segmented fiber reinforcementis used, a scoring or cutting step may be employed after it is made intoa gel sheet to obtain clean edges of segment gaps.

The segmented reinforcement in a sheet form useful in the presentinvention may be of several types. Non-wovens of several types made withcontinuous fibers, or chopped fibers may be used. When chopped fibersare used, in some embodiments, the non-woven may contain binders. Inanother embodiment, the non-woven sheets useful in the present inventionmay be needle-punched to form felt-like materials. The above describedmaterials may be segmented by scoring them across their thickness usinga knife, hot knife, saw blade or any other scoring technique known inthe art. The fibers useful to prepare the fiber-reinforcements of thepresent invention includes, mineral wool, glass wool, fiber glass,polyester, polyolefin terephthalates, poly(ethylene) naphthalate,polycarbonates and Rayon, Nylon, cotton based lycra (manufactured byDuPont), Carbon based fibers like graphite, precursors for carbon fiberslike polyacrylonitrile (PAN), oxidized PAN, uncarbonized heat treatedPAN such as the one manufactured by SGL carbon, fiberglass basedmaterial like S-glass, 901 glass, 902 glass, 475 glass, E-glass, silicabased fibers like quartz, quartzel (manufactured by Saint-Gobain),Q-felt (manufactured by Johns Manville), Saffil (manufactured bySaffil), Durablanket (manufactured by Unifrax) and other silica fibers,Polyaramid fibers like Kevalr, Nomex, Sontera (all manufactured byDuPont) Conex (manufactured by Taijin), polyolefins like Tyvek(manufactured by DuPont), Dyneema (manufactured by DSM), Spectra(manufactured by Honeywell), other polypropylene fibers like Typar,Xavan (both manufactured by DuPont), fluoropolymers like PTFE with tradenames as Teflon (manufactured by DuPont), Goretex (manufactured byGORE), Silicon carbide fibers like Nicalon (manufactured by COICeramics), ceramic fibers like Nextel (manufactured by 3M), Acrylicpolymers, fibers of wool, silk, hemp, leather, suede, PBO—Zylon fibers(manufactured by Tyobo), Liquid crystal material like Vectan(manufactured by Hoechst), Cambrelle fiber (manufactured by DuPont),Polyurethanes, polyamaides, Wood fibers, Boron, Aluminum, Iron,Stainless Steel fibers and other thermoplastics like PEEK, PES, PEI,PEK, PPS and combinations thereof.

In addition to the fiber materials described in the present invention,foam materials and in specific embodiments, rigid foam boards may bemade into segmented sheets using a face sheet and processed using thetechniques described in this application, thus produced gel-foam rigidcomposite sheets that may be further be made into rigid panels asdescribed above. In another embodiment, the foam materials may be openpore foams.

In general, the gel precursors useful in the present invention comprisemetal oxides that are compatible with the sol-gel process where uponpolymerization form a gel network(s). The silica precursors used may bechosen from but are not limited to: alkoxysilanes, partially hydrolyzedalkoxysilanes, tetraethoxylsilane (TEOS), partially hydrolyzed TEOS,condensed polymers of TEOS, tetramethoxylsilane (TMOS), partiallyhydrolyzed TMOS, condensed polymers of TMOS, tetra-n-propoxysilane,partially hydrolyzed and/or condensed polymers of tetra-n-propoxysilane,or combinations thereof. TEOS, partially hydrolyzed polyethysilicates,and polyethylsilicates are some of the more common commerciallyavailable silica precursors. The fillers may be dispensed in the gelprecursor solution at any point before a gel is formed. Gel formationmay be viewed as the point where a solution (or mixture) exhibitsresistance to flow and/or forms a continuous polymeric networkthroughout its volume. Preferably the mixture comprising fillers andprecursors is a homogenous solution, conducive to gel formation. Inaddition to the silica based precursors, precursors of zirconia, yttria,hafnia, alumina, titania, ceria are useful. In additional embodiments,organic precursors such as polyacrylates, polystyrenes,polyacrylonitriles, polyurethanes, polyimides, polyfurfural alcohol,phenol furfuryl alcohol, melamine formaldehydes, resorcinolformaldehydes, cresol formaldehyde, phenol formaldehyde, polyvinylalcohol dialdehyde, polycyanurates, polyacrylamides, various epoxies,agar, and agarose and combinations of the above may be used as gelprecursors in the present invention. Additionally, hybridorganic-inorganic gel precursors with various combinations of thespecies described above may be used.

Suitable solvents for use herein include: lower alcohols with 1 to 6carbon atoms, preferably 2 to 4, although other solvents can be used asis known in the art. Ethanol, is typically a favored solvent used.Examples of other useful solvents include but are not limited to: ethylacetate, ethyl acetoacetate, acetone, dichloromethane, tetrahydrofuran,methanol, isopropyl alcohol and the like. Of course in order to achievea desired level of dispersion or solution certain gel precursor/fillersystems, or a multi-solvent approach may be required.

Generally, gels may be formed via maintaining the mixture in a quiescentstate for a sufficient period of time, changing the pH of the solution,directing a form of energy onto the mixture, or a combination thereof.Exemplary forms of energy include: a controlled flux of electromagnetic(ultraviolet, visible, infrared, microwave), acoustic (ultrasound), orparticle radiation. In the present invention the gel is formed after thegel precursor is combined with the segmented reinforcements of thepresent invention.

Gels may be additionally aged prior to drying to further strengthen thegel structure by increasing the number of cross-linkages. This procedureis useful for preventing potential volume loss during drying, or simplya stronger final gel. Aging can involve: maintaining the gel (prior todrying) at a quiescent state for an extended period, maintaining the gelat elevated temperatures, addition of cross-linkage promoting compoundsor any combination thereof. Aging time period typically requires betweenabout 1 hr and several days. The preferred temperatures are usuallybetween about 10° C. and about 100° C. Additionally, surfacehydrophobicity imparting agents such as hexamethyldisilazane,hexamethyldisiloxane, trimethylethoxysilane, methylethoxysilane,methylmethoxy silane, propyltriethoxysilane, propyltrimethoxysilane,trimethylchlorosilane, trimethylmethoxysilane, triethylethoxysilane,tri-ethylmethoxysilane, dimethyldichlorosilane, dimethyldiethoxysilane,methyltrichlorosilane, ethyltrichlorosilane, may be used to render thegel/fiber composites hydrophobic. Such agents may be mixed with asolvent such as the solvent used in the prior steps and flowed throughthe rolled gel sheets during the aging step as described above.

Drying plays an important role in engineering the properties ofaerogels, such as porosity and density which influence the materialthermal conductivity. To date, numerous drying methods have beenexplored. U.S. Pat. No. 6,670,402 teaches drying via rapid solventexchange of solvent(s) inside wet gels using supercritical CO₂ byinjecting supercritical, rather than liquid, CO₂ into an extractor thathas been pre-heated and pre-pressurized to substantially supercriticalconditions or above to produce aerogels. U.S. Pat. No. 5,962,539describes a process for obtaining an aerogel from a polymeric materialthat is in the form a sol-gel in an organic solvent, by exchanging theorganic solvent for a fluid having a critical temperature below atemperature of polymer decomposition, and supercritically drying thefluid/sol-gel. U.S. Pat. No. 6,315,971 discloses processes for producinggel compositions comprising: drying a wet gel comprising gel solids anda drying agent to remove the drying agent under drying conditionssufficient to minimize shrinkage of the gel during drying. Also, U.S.Pat. No. 5,420,168 describes a process whereby Resorcinol/Formaldehydeaerogels can be manufactured using a simple air drying procedure.Finally, U.S. Pat. No. 5,565,142 herein incorporated by referencedescribes subcritical drying techniques. The embodiments of the presentinvention can be practiced with drying using any of the abovetechniques. In some embodiments, it is preferred that the drying isperformed at vacuum to below super-critical pressures (pressures belowthe critical pressure of the fluid present in the gel at some point) andoptionally using surface modifying agents. In another embodiment, thedrying is accomplished using supercritical CO2. Thus dried gel-fibercomposites may be further dried by passing through an oven at elevatedtemperatures.

Various performance enhancing additives may be added to thegel-precursor before the gel is formed in the various embodiments of thepresent invention. They include of titanium dioxide, iron oxides, carbonblack, graphite, aluminum hydroxide, phosphates, borates, metalsilicates, metallocenes, molybdates, stannates, hydroxides, carbonates,zinc oxides, aluminum oxides, antimony oxides, magnesium-zinc blends,magnesium-zinc-antimony blends, silicon carbide, molybdenum silicide,manganese oxides, iron titanium oxide, zirconium silicate, zirconiumoxide, iron (I) oxide, iron (III) oxide, manganese dioxide, irontitanium oxide (ilmenite), chromium oxide and a combination thereof.

EXAMPLES

The following example illustrates the preparation and performance of asegmented gel-fiber composites and an aerogel-based rigid panel inaccordance with the above invention. Precise longitudinal segmentationof a commercially available glass wool non-woven sheet with anintegrated face sheet, was accomplished via the use of utility knife orautomated rotary tool in combination with a custom produced cutting jigaimed at accomplishing a cut depth of no less than 90% of the originalthickness. Using this method, segmented glass wool sheets measuring36″×8″ were produced with both 1″ and 2″ segments. A requisite amount ofa soluble silica source (i.e. sol comprising hydrolyzedtetraethoxysilane and its derivatives) and condensation catalyst,aqueous ammonium hydroxide, were combined and allowed to penetrate theglass-wool non-woven sheet in a horizontal/flat configuration. After asyneresis period of 15 minutes the gel/fiber composite was wound arounda mandrel possessing a 6″ diameter. The rolling of such a composite wasaccomplished by ensuring that the segment gaps were facing away from themandrel during winding. In such a way, the stresses of winding wererelieved as gaps are formed along each segmentation. The gel/fibercomposite in the cylindrical form was then subject to a period of agingin which the rolled composite was exposed to a hot ethanol solution ofammonium hydroxide and a hydrophobic agent containing alkyl and silylgroups (hexamethyldisilazane). After aging, the rolled composite wastransferred to a cylindrical pressure vessel and was then dried usingsupercritical CO2 extraction to remove the solvent.

The composite was then treated with heat to remove any residual moistureand/or volatiles. The material was then unwound horizontally to adopt aflat configuration. The heat treatment may also be applied after thecomposite was unrolled. After unwinding the composite, an organic basedadhesive (Spray 78 or FastBond) was spray applied (to the aerogel side)at a nominal coat weight of 20-40 g/m2. A second piece of segmentedgel/fiber composite, processed in the same manner was then attached tothe first piece such that the segmentations are staggered and that theface sheets are orientated away from the bonding face. The material wasthen subject to a short period of compressive stress (<0.25 PSI) toensure complete mating and curing of the adhesive. The compressivestress was then relieved and the resulting rigid panel was characterizedfor thermal conductivity. The following table provides the measuredthermal conductivity of the rigid panels thus formed at two differenttemperatures while under a slight pressure of 2 psi.

Thermal Conductivity (mW/mK) Segment Size 10° C. 37.5° C. 1″ 14.7 16.12″ 14.7 15.8

Example 2

One can also fabricate the segmented fiber reinforcements describedabove using any combination of binder containing fiber reinforcement andlightweight face sheets. For instance, a series of segmented fiberreinforcements suitable for aerogel production were produced using KnaufBatt Insulation (0.5″, 2 lb/ft3) and a glass veil face sheet with adensity of 10 g/m2. These fiber reinforcements were fabricated using atwo-step process involving the initial lamination of the face sheet toone side of the fiberglass batt using an acrylic based adhesive(Fastbond) along the entire length of the insulation batt, followed by aprecise longitudinal segmentation to no less than 90% of the originalthickness using a utility knife and/or automated rotary tool. Thelongitudinal segmentation was carried out in such a fashion to leave thelaminated face sheet intact. Segmentation length was varied between 1″and 6″.

Using such pre-fabricated segmented materials, a series of aerogelcomposites measuring 12″×24″ were prepared in a horizontalconfiguration. Infiltration of a requisite amount of soluble silicasource (i.e. sol comprising hydrolyzed tetraethoxysilane and itsderivatives) and a suitable condensation catalyst were allowed topenetrate the fiber reinforcement pre-fabricated at a segmentationinterval of 2 inches. After a syneresis period of 15 minutes thegel/fiber composite was wound around a mandrel possessing a 6″ diameter.The rolling of such a composite was accomplished by ensuring that thesegment gaps were facing away from the mandrel during winding. In such away, the stresses of winding were relieved as gaps are formed along eachsegmentation. The gel/fiber composite in the cylindrical form was thensubject to a period of aging in which the rolled composite was exposedto a hot ethanol solution of ammonium hydroxide and a hydrophobic agentcontaining alkyl and silyl groups (hexamethyldisilazane). After aging,the rolled composite was transferred to a cylindrical pressure vesseland was then dried using supercritical CO2 extraction to remove thesolvent. The composite was then treated with heat to remove any residualmoisture and/or volatiles. The dried aerogel material was then unwoundhorizontally to adopt a flat configuration. After unwinding thecomposite, an organic based adhesive (Spray 78 or FastBond that may beobtained from 3M, Minneapolis, Minn.) was spray applied (to the aerogelside) at a nominal coat weight of 20-40 g/m2. A second piece ofsegmented gel/fiber composite, processed in the same manner was thenattached to the first piece such that the segmentations are staggeredand that the face sheets are orientated away from the bonding face. Thematerial was then subject to a short period of compressive stress (<0.25PSI) to ensure complete mating and curing of the adhesive. Thecompressive stress was then relieved and the resulting rigid panel wascharacterized for thermal conductivity. The following table provides themeasured thermal conductivity of the rigid panels produced inquadruplicate at two different mean test temperatures.

Thermal Thermal Conductivity at Conductivity at Thickness 10 C. 37.5 C.ID (mm) (mW/mK) (mW/mK) Segmented Knauf Panel 1 23.9 14.1 15.3 SegmentedKnauf Panel 2 23.9 14.7 16.6 Segmented Knauf Panel 3 24.2 14.6 17.1Segmented Knauf Panel 4 24.9 14.4 16.3

Example 3

Prefabricated segmented reinforcements is produced via the lamination ofdiscontinuous pieces of fiber reinforcement to a suitable lightweightface sheet. A wide range of materials such as mineral wool slab,fiberglass batts, or rigid open celled-foams are cut longitudinally intodiscontinuous pieces at the preferred segmentation intervals of 1″ to 6″and then laminated to a suitable face sheet to produce a segmentedproduct suitable for aerogel production as described above in Example 1.Aerogel products and panels are produced with such reinforcements usingthe techniques outlined in Examples 1-2.

Example 4

The lightweight fibrous face sheets used in examples 1-3 isalternatively replaced with any chemically compatible polymericfilms/laminates. Laminates with thermoplastic tie layers are heat set toa single side of continuous batts of fibrous insulation followed aprecise longitudinal segmentation to a depth of no less than 90% of theoriginal thickness. Polymeric films are applied via the application of anon-aqueous or aqueous coating, followed by appropriate cure methods toform a substantially continuous polymeric film with a suitablethickness. Longitudinal segmentation is conducted after film formationto produce segmented fiber reinforcement suitable for aerogel productionusing the experimental techniques outlined in Examples 1-2.

1. A process comprising the steps of: providing a segmentedreinforcement sheet comprising a segmented fiber reinforcement sheet ora segmented open-cell foam reinforcement sheet; combining the segmentedreinforcement sheet with a gel precursor; gelling the gel precursor inthe segmented reinforcement sheet to make a segmented reinforced gelcomposite sheet; and drying the segmented reinforced gel composite sheetto make a reinforced aerogel composite sheet.
 2. The process of claim 1further comprising the step of applying an adhesive to at least one faceof the reinforced aerogel composite sheet and attaching it to anotherplanar material.
 3. The process of claim 1, further comprising the stepsof: providing the reinforced aerogel composite sheet of claim 1 with atleast two major surfaces and multiple segmented cross-sectionalsurfaces; applying an adhesive to at least one surface of saidreinforced aerogel composite sheet; and attaching the reinforced aerogelcomposite sheet to another aerogel composite sheet.
 4. (canceled)
 5. Theprocess of claim 1 wherein the segmented reinforcement sheet has afacing layer or sheet attached to it.
 6. The process of claim 5 whereinfacing layer comprises fibers.
 7. The process of claim 1 wherein thesegmented reinforcement sheet comprises a segmented fiber reinforcementsheet which comprises non-continuous fibers.
 8. The process of claim 1further comprising the step of incorporating additives selected from thegroup consisting of titanium dioxide, iron oxides, carbon black,graphite, aluminum hydroxide, phosphates, borates, metal silicates,metallocenes, molybdates, stannates, hydroxides, carbonates, zincoxides, aluminum oxides, antimony oxides, magnesium-zinc blends,magnesium-zinc-antimony blends, silicon carbide, molybdenum silicide,manganese oxides, iron titanium oxide, zirconium silicate, zirconiumoxide, iron (II) oxide, iron (III) oxide, manganese dioxide, irontitanium oxide (ilmenite), chromium oxide and a combination thereof. 9.The process of claim 1, wherein the segmented reinforcement sheetcomprises a segmented fiber reinforcement sheet, and the process furthercomprising the step of adding at least a binder to the fibers of thefiber reinforcement sheet or using a fiber reinforcement sheetcomprising at least one binder.
 10. The process of claim 1, wherein atleast a segment of the segmented reinforcement material is rigid. 11.The process of claim 1, wherein the gel precursor comprises a materialselected from the group consisting of zirconia, yttria, hafnia, alumina,titania, ceria, silica, polyacrylates, polystyrenes, polyacrylonitriles,polyurethanes, polyimides, polyfurfural alcohol, phenol furfurylalcohol, melamine formaldehydes, resorcinol formaldehydes, cresolformaldehyde, phenol formaldehyde, polyvinyl alcohol dialdehyde,polycyanurates, polyacrylamides, various epoxies, agar, and agarose andcombinations thereof.
 12. The process of claim 1 wherein the segmentedreinforcement sheet comprises a segmented fiber reinforcement sheetcomprising materials selected from the group consisting of mineral wool,glass wool, fiber glass, polyester, polyolefin terephthalates,poly(ethylene) naphthalate, polycarbonates, cellulose fiber, aliphaticpolyamides, cotton based polyester-polyurethanes, Carbon based fibers,graphite, polyacrylonitrile (PAN), oxidized PAN, uncarbonized heattreated PAN, fiberglass based material, E-glass, silica based fibers,quartz, Polyaramid fibers, polyolefins, polypropylene fibers,fluoropolymers, polytetrafluoroethylene (PTFE), Silicon carbide fibers,ceramic, Acrylic polymers, fibers of wool, silk, hemp, leather, suede,poly(p-phenylene-2,6-benzobisoxazole) (PBO), Liquid crystal material,Polyurethanes, polyamaides, Wood fibers, Boron, Aluminum, Iron,Stainless Steel fibers, polyether ether ketone (PEEK), polyether sulfone(PES), polyetherimide (PEl), polyether ketone (PEK), poly(p-phenylenesulfide) (PPS) and combinations thereof.
 13. The process of claim 3wherein the adhesive is selected from the group consisting of potassiumwater glass, sodium water glass, cement and alkali-activatedaluminosilicates, polyethylene, kapton, polyurethane, polyester, naturalrubber, synthetic rubber, hypalon, plastic alloys, PTFE, polyvinylhalides, polyester, neoprene, acrylics, nitriles, EPDM, EP, viton,vinyls, vinyl-acetate, ethylene-vinyl acetate, styrene,styrene-acrylates styrene-butadienes, polyvinyl alcohol,polyvinylchloride, acrylamids, phenolics and combinations thereof. 14.The process of claim 1, wherein the thermal conductivity of thereinforced aerogel composite sheet is less than 25 mW/mK at ambientconditions.
 15. The process of claim 1, further comprising the step ofrolling the segmented reinforced gel composite sheet prior to dryinginto a roll having an axis, and wherein the rolling of the gel compositesheet is such that gaps formed between the segments face away from theaxis of the roll.
 16. A reinforced aerogel composite sheet made by theprocess of claim
 1. 17. A panel comprising at least two layers ofreinforced aerogel composites wherein at least one layer comprises thereinforced aerogel composite sheet of claim
 16. 18. The panel of claim17, further comprising an adhesive, wherein the adhesive is selectedfrom the group consisting of potassium water glass, sodium water glass,cement and alkali-activated aluminosilicates, polyethylene, kapton,polyurethane, polyester, natural rubber, synthetic rubber, hypalon,plastic alloys, PTFE, polyvinyl halides, polyester, neoprene, acrylics,nitriles, EPDM, EP, viton, vinyls, vinyl-acetate, ethylene-vinylacetate, styrene, styrene-acrylates styrene-butadienes, polyvinylalcohol, polyvinylchloride, acrylamids, phenolics and combinationsthereof.
 19. The reinforced aerogel composite sheet of claim 16, whereinthe thermal conductivity of the reinforced aerogel composite is lessthan 25 mW/mK at ambient conditions.
 20. The panel of claim 17, whereinthe thermal conductivity of the reinforced aerogel composite is lessthan 25 mW/mK at ambient conditions.